This invention relates to an Asynchronous Transfer Mode (ATM) traffic controlling apparatus and an ATM traffic controlling method for controlling a traffic of multiplexed multimedia information such as sound, data, image, and so on, which is transmitted in asynchronous transfer mode.
The ATM has become the focal point of attention as the mainstream technology for a wide area Integrated Service Digital Network or ISDN.
FIG. 28 shows the structure of a cell used for ATM.
A cell 2801 to be used for ATM, a cell header 2802 which contains controlling information of cell 2801, and cell information 2803 having data information and sound information of cell 2801 are shown in FIG. 28. For ATM, any information in cell information 2803, such as sound, data, image, facsimile, etc., is partitioned into a fixed length in cell information 2803. The cell information 2803 is provided with cell header 2802 which contains logical channel (Virtual Call Indicator (VCI)) information, etc., required for switching cell 2801. The cell header and the cell information form the cell 2801. This cell 2801 format enables integrated transmission. Particularly, for a private in-house communication, where sound communication and inter-local area network (LAN) communication are the typical form of data communication, it is expected that the integration of this traffic and the ATM technology will help construct a more efficient transmission network than ever before.
FIG. 29 shows an example of the network configuration of sound/data integrated network using ATM.
In FIG. 29, an ATM multiplexed transmitter 2901, an ATM switched network 2902, a data ATM terminal 2903 for setting data connection and sending data cells, a sound ATM terminal 2904 for setting sound connection and sending sound cells, a private data traffic ATM line 2905, a private sound traffic ATM line 2906, a wide area ATM line 2907 for connecting ATM multiplexed transmitter 2901 and ATM switched network 2902, a data traffic ATM line terminating unit 2908, provided in ATM multiplexed transmitter 2901, to be connected to data ATM terminal 2903 via private data traffic ATM line 2905, a sound traffic ATM line terminating unit 2909, provided in ATM multiplexed transmitter 2901, to be connected to sound ATM terminal 2904 via private sound traffic ATM line 2906, and a multiplexed transmitting unit 2910 provided in ATM multiplexed transmitter 2901 are illustrated.
Next, the operation is explained.
In ATM multiplexed transmitter 2901, a cell received by data-system ATM line terminating unit 2908 and a cell received by sound-system ATM line terminating unit 2909 are multiplexed by multiplexed transmitting unit 2910, and sent to wide area ATM line 2907.
An efficient use of wide area ATM line 2907, shown in FIG. 29 is required for in-house communication. Because about 50 percent of sound communication is normally soundless, sound ATM terminal 2904 transmits sound information (hereinafter called a sound cell) consisting of only sound by private sound traffic ATM line 2906 at every cell forming cycle (a cycle being a time period during which sound is transformed into a cell), and tries not to transmit soundless portion so as to increase line efficiency.
Meanwhile, because real-time is generally in higher demand in sound communication than in data communication, ATM multiplexed transmitter 2901 gives preference to sending sound cells transmitted by sound ATM terminal 2904 to wide area ATM line 2907. The data information (hereinafter a data cell) transmitted by data ATM terminal 2903 is transmitted to wide area ATM line 2907 using idle time during which no sound cell to be sent exists.
A method of realizing the conventional multiplexed transmitting unit 2910 for sound and data multiplexed transmission in ATM is set forth in Analysis and Engineering of A Voice/Data Packet Multiplexer of IEEE Transaction of Communication Vol.41 No. 11, pages 1656 to 1667.
FIG. 30 shows a configuration of the conventional multiplexed transmitting unit 2910, where, a sound/data identifying unit 3001 for identifying whether a received cell is sound or data, a data cell transmitting buffer 3002 for storing data cells for transmission, a sound cell transmitting buffer 3003 for storing sound cells for transmission, a transmitting circuit 3004 for transmitting sound or data cells, a receiving circuit 3005 for receiving sound or data cells, and a receiving buffer 3006 for storing sound or data cells received by receiving circuit 3005 are depicted.
The operation is explained next.
In FIG. 30, sound/data identifying unit 3001 identifies whether or not a cell is a sound cell or a data cell upon its arrival from data traffic ATM line terminating unit 2908 or sound traffic ATM line terminating unit 2909. A sound cell is stored in sound cell transmitting buffer 3003 and a data cell is stored in data cell transmitting buffer 3002.
Then, transmitting circuit 3004 reads the sound cell from sound cell transmitting buffer 3003 and transmits into wide area ATM line 2907. If no sound cell is stored in transmitting buffer 3003 and the data cells are stored in data cell transmitting buffer 3002, the data cells are read and transmitted into wide area ATM line.
Meanwhile, cells arriving from other terminals by way of wide area ATM line 2907 are received by receiving circuit 3005 and stored in receiving buffer 3006, and then transmitted to data traffic ATM line terminating unit 2908 or sound traffic ATM line terminating unit 2909. Sound and data multiplexed transmission is realized in this way by giving preferential transmission to sound cells using separated buffers.
However, when the volume of traffic of sound cells grows heavy, the probability for data cells being kept waiting in the data cell transmitting buffer increases, which may result in buffer overflow destroying part of cells if the capacity of the data cell transmitting buffer is insufficient. On the other hand, in order to suppress the cell disposal rate within an appropriate range in an event of buffer overflow, a large capacity is required for the data cell transmitting buffer.
For the application of ATM to a wide area network data communication such as inter-LAN communication, it is recently become known that communication efficiency gets degraded significantly if the cell disposal rate could not be suppressed. ABR Service Class Quality Assessment by the National Convention for Electronics Information Communication Academy SB-10-5 in 1996, presented with an effective measure using a data terminal capable of adjusting a transmission rate depending on the network load.
FIG. 31 is a diagram showing an adjustment sequence of the transmission rate. It shows the transmission sequence of data ATM terminal 2903a in normal mode.
FIG. 32 shows an adjustment sequence of the transmission rate for data ATM terminal 2903a in abnormal mode.
FIG. 33 shows the structure of a data traffic control cell (hereinafter an RM cell) format for controlling the data traffic indicated in sequences of FIGS. 31 and 32.
In FIG. 33, a cell 3301, a header 3302 indicating the RM cell, information 3303 of cell 3301, and a transfer rate specified value 3304 included in information 3303 are illustrated.
How to adjust the transmission rate is discussed below with reference to FIG. 31.
Data ATM terminal 2903a on the transmitting side is assumed to have a predetermined number of times (Nrmxe2x88x921). Nrm indicates the ratio of transmitting RM cells, e.g., the number of cells per RM interval. Each time the predetermined number of times (Nrmxe2x88x921) of data cells are transmitted, an RM cell (called a forward RM cell) is transmitted once. Data ATM terminal 2903b on the receiving side returns a RM cell (called a backward RM cell) to data ATM terminal 2903a on the transmitting side. The backward RM cell contains transfer rate specified value 3304 indicated as the valid transmission rate by data ATM terminal 2903a shown in FIG. 33.
In FIG. 31, cycle Td is a cycle to change the transmission rate of data ATM terminal 2903a. Because cycle Td depends on the ratio Nrm for transmitting the RM cells, cycle Td dynamically changes with the changes in the transmission rate.
In returning the backward RM cell, data ATM terminal 2903b on the receiving side sets a transfer rate that can be processed by its own as transfer rate specified value 3304 shown in FIG. 33. When the backward RM cell is returned to data ATM terminal 2903a on the transmitting side via ATM multiplexed transmitter 2901 or ATM switched network 2902, if the set transfer rate specified value 3304 exceeds the transfer rate that can be processed by ATM multiplexed transmitter 2901 or ATM switched network 2902, the ATM multiplexed transmitter 2901 or ATM switched network 2902 hereinafter the ATM multiplexed transmitter 2901 or ATM switched network 2902 may be referred to as the node) resets transfer rate specified value 3304 of the RM cell to the transfer rate that can be processed by its own, and relays.
When the backward RM cell has arrived at the transmitting side, the minimum transfer rate that can be processed by the nodes provided for the route through which the cell passes is designated as transfer rate specified value 3304. In other words, for transfer rate specified value 3304 of the RM cells, the transfer rate that can be processed by a bottleneck node of the route is specified. Upon reception of the backward RM cell, data ATM terminal 2903a adjusts the cell transmission interval according to the transfer rate specified value 3304 of the received cell, and continues transmission.
The transfer controlling which dynamically follows up the networking condition is thereby realized.
FIG. 32 shows an adjustment sequence when the backward RM cell would not be sent to the transmitting side for some reason. In such a case, if the backward RM cell cannot be received even when data ATM terminal 2903a sends the forward RM cell based on the designated number of times (hereinafter Crm. Crm means the number of outstanding forward RM cells allowed before cutoff.), the cell is transmitted by lowering transmission rate. That is, when the backward RM cell cannot be received, the transmission rate is automatically suppressed judging that network congestion has occurred. This mechanism thus automatically suppresses congestion.
Such method for data ATM terminal 2903 of controlling the transmission rate allows the adjustment of the transfer rate according to the networking condition. ATM multiplexed transmitter 2901 or ATM switched network 2902 can prevent congestion without requiring a large buffer. However, in order for this mechanism to work, the nodes of the network, namely, ATM multiplexed transmitter 2901 or ATM switched network 2902 must be able to grasp the transfer rate they can handle, and specify the rate to the transmission terminals. Although an accurate controlling is required for an in-house communication network, for which the efficient use of wide area ATM line 2907 is vital, there were no effective measures.
The conventional ATM multiplexed transmitter has a problem of requiring a large buffer for suppressing the disposal rate of data cells, because sound cells were transmitted in preference to data cells in the conventional art of sound and data multiplexed transmission.
In addition, the data terminal on the transmitting side lacks an ATM traffic controlling unit for adjusting the transmission rate, so as to make the nodes, such as the ATM multiplexed transmitter or the ATM switched network, tailor the transmission rate that they can process.
This invention aims at overcoming above-mentioned problems. It aims at realizing an ATM traffic controlling apparatus and an ATM traffic controlling method for keeping the disposal rate of data cells within an appropriate range when traffic from data terminals grows heavy, without requiring a large buffer.
The ATM traffic controlling apparatus of this invention is characterized by an ATM traffic controlling apparatus, incorporated in an ATM multiplexed transmitter, for accommodating a plurality of sound connections for transferring sound information using sound cells among sound ATM terminals and a data connection for transferring data information to be communicated among data ATM terminals using data cells and data traffic controlling cells (hereinafter RM cells) in an ATM line may comprise a transmission rate determining unit for monitoring an arriving condition of the sound cells for the plurality of sound connections being sent from sound ATM terminals at a determined cycle, for predicting a number of sound cells to be arriving at a next cycle and for determining a transmission rate of a data traffic; and a transmission rate changing unit for receiving the data traffic controlling cells from the ATM line, for setting the transmission rate to the data traffic controlling cells, and for transmitting to the data ATM terminal.
The ATM traffic controlling apparatus of this invention is characterized by the ATM traffic controlling apparatus which may comprise a transmitting buffer for receiving the data cells from the data ATM terminal and the sound cells from the sound ATM terminals, and for storing the cells, a transmitting circuit for transmitting the cells from the transmitting buffer, a rate calculation circuit for obtaining a prediction coefficient based on the number of sound connections connected simultaneously, and for calculating a transferable rate based on the prediction coefficient and the number of sound cells to be arriving, an RM cell processing circuit for processing the RM cells including a transfer rate specified value which specifies a transfer rate for the data ATM terminal on a transmitting side, a receiving circuit for receiving the cells, and a receiving buffer for storing received data cells, and wherein the RM cell processing circuit may replace the transfer rate specified value in the RM cells with the transferable rate from the rate calculation circuit when the transferable rate from the rate calculation circuit is smaller than the transfer rate specified value in the RM cell.
The ATM traffic controlling apparatus of this invention is characterized by the ATM traffic controlling apparatus, wherein the rate calculation circuit may judge whether the sound cells are used as a sound band data, monitor the arriving condition, respectively for the sound cells having the sound information and for the sound cells of the sound band data, predict the number of sound cells to be arriving at the next cycle based on a monitored result, and may determine the transmission rate of the data traffic.
The ATM traffic controlling apparatus of this invention is characterized by the ATM traffic controlling apparatus which may comprise a transmitting buffer for storing the data cells from the data ATM terminal and sound cells from the sound ATM terminals, a transmitting circuit for transmitting the cells from the transmitting buffer, a signaling monitor circuit for monitoring a signaling information, and for providing the number of sound connections (hereinafter called the number of simultaneous connections) connected simultaneously based on the signaling information, a rate calculation circuit for obtaining a prediction coefficient based on the number of simultaneous connections, and calculating a transferable rate based on the prediction coefficient and the number of sound cells to be arriving, a RM cell processing circuit for processing the RM cells including a transfer rate specified value for specifying a transfer rate to the data ATM terminals on a transmitting side, a receiving circuit for receiving the cells, and a receiving buffer for storing received data cells.
The ATM traffic controlling apparatus of this invention is characterized by the ATM traffic controlling apparatus, wherein the rate calculation circuit may predict the arriving condition of the sound cells at the next cycle based on the number of simultaneous connections, when the number of simultaneous connections of the sound connection may exceed a specified value.
The ATM traffic controlling apparatus of this invention is characterized by the ATM traffic controlling apparatus, wherein the rate calculation circuit may predict a cycle for which the data ATM terminal changes the transmission rate and the number of cells to be arriving at this cycle based on the arriving condition of the sound cells.
The ATM traffic controlling apparatus of this invention is characterized by the ATM traffic controlling apparatus which may comprise a transmitting buffer for receiving the data cells from the data ATM terminal and the sound cells from the sound ATM terminals, and storing the cells, a transmitting circuit for transmitting the cells from the transmitting buffer, a rate calculation circuit for obtaining a prediction coefficient based on the number of sound connections connected simultaneously, and for calculating a transferable rate based on the prediction coefficient and the number of sound cells to be arriving, a RM cell processing circuit for processing the RM cells including a transfer rate specified value with which to specify a transfer rate to the data ATM terminal on a transmitting side, a receiving circuit for receiving the cells, a receiving buffer for storing received data cells, and a data monitor circuit for monitoring the arriving condition of the data cells and for calculating a cycle for which the data terminals change the transmission rate.
The ATM traffic controlling apparatus of this invention is characterized by the ATM traffic controlling apparatus, wherein the RM cell processing circuit may monitor the arriving condition of a backward RM cell, and when the backward RM cell may not be detected, the RM cell processing circuit may automatically transmit the backward RM cell.
The ATM traffic controlling apparatus of this invention is characterized by the ATM traffic controlling apparatus, wherein the RM cell processing circuit may monitor the arriving condition of the data connections for the data connection, and obtain a cycle for which the data ATM terminals change the transmission rate when a backward RM cell is not detected and a changed rate.
The ATM traffic controlling apparatus of this invention is characterized by the ATM traffic controlling apparatus, wherein the rate calculation circuit may automatically correct the prediction coefficient for calculating the number of sound cells to be arriving at the next cycle based on the arriving condition of the sound cells for the plurality of sound connections.
The ATM traffic controlling apparatus of this invention is characterized by the ATM traffic controlling apparatus, wherein the rate calculation circuit may include buffers for storing the sound cells and the data cells separately, and determine the transmission rate of the data traffic based on a storing condition of the data cells and the arriving condition of the sound cells in the plurality of sound connections.
An ATM traffic controlling method of this invention is characterized by an ATM traffic controlling method, incorporated in an ATM multiplexed transmitter, for accommodating a plurality of sound connections for transferring sound information using sound cells among sound ATM terminals and a data connection for transferring data information to be communicated among data ATM terminals using data cells and data traffic controlling cells hereinafter RM cells) in an ATM line may comprise a transmission rate determining step for monitoring an arriving condition of the sound cells for the plurality of sound connections being sent from the sound ATM terminals at a determined cycle, for predicting a number of sound cells to be arriving at a next cycle and for determining a transmission rate of a data traffic, and a transmission rate changing step for receiving the data traffic controlling cells from the ATM line, for setting the transmission rate to the data traffic controlling cells, and for transmitting to the data ATM terminal.
The ATM traffic controlling method of this invention is characterized by the ATM traffic controlling method which may comprise a transmitting buffer step for receiving the data cells from the data ATM terminal and the sound cells from the sound ATM terminals, and for storing the cells, a transmitting step for transmitting the cells from the transmitting buffer, a rate calculation step for obtaining a prediction coefficient based on the number of sound connections connected simultaneously, and for calculating a transferable rate based on the prediction coefficient and the number of sound cells to be arriving, an RM cell processing step for processing the RM cells including a transfer rate specified value which specifies a transfer rate for the data ATM terminal on a transmitting side, a receiving step for receiving the cells, and a receiving buffer step for storing received data cells, and wherein the RM cell processing step may replace the transfer rate specified value in the RM cells with the transferable rate from the rate calculation circuit when the transferable rate from the rate calculation circuit is smaller than the transfer rate specified value in the RM cell.
The ATM traffic controlling method of this invention is characterized by the ATM traffic controlling method, wherein the rate calculation step may judge whether the sound cells may be used as a sound band data, monitor the arriving condition, respectively for the sound cells having the sound information and for the sound cells of the sound band data, predict the number of sound cells to be arriving at the next cycle based on a monitored result, and determine the transmission rate of a data traffic.
The ATM traffic controlling method of this invention is characterized by the ATM traffic controlling method which may comprise a transmitting buffer step for storing the data cells from the data ATM terminal and the sound cells from the sound ATM terminals, a transmitting step for transmitting the cells from the transmitting buffer, a signaling monitor step for monitoring a signaling information, and for providing the number of sound connections (hereinafter called the number of simultaneous connections) connected simultaneously based on the signaling information, a rate calculation step for obtaining a prediction coefficient based on the number of simultaneous connections, and calculating a transferable rate based on the prediction coefficient and the number of sound cells to be arriving, a RM cell processing step for processing the RM cells including a transfer rate specified value for specifying a transfer rate to the data ATM terminals on a transmitting side, a receiving step for receiving the cells, and a receiving buffer step for storing received data cells.
The ATM traffic controlling method of this invention is characterized by the ATM traffic controlling method, wherein the rate calculation step may predict the arriving condition of the sound cells at the next cycle based on the number of simultaneous connections, when the number of simultaneous connections of the sound connection may exceed a specified value.
The ATM traffic controlling method of this invention is characterized by the ATM traffic controlling method, wherein the rate calculation circuit may predict a cycle for which the data ATM terminal changes the transmission rate and the number of cells to be arriving at this cycle based on the arriving condition of the sound cells.
The ATM traffic controlling method of this invention is characterized by the ATM traffic controlling method may comprise a transmitting buffer step for receiving the data cells from the data ATM terminal and the sound cells from the sound ATM terminals, and storing the cells, a transmitting step for transmitting the cells from the transmitting buffer, a rate calculation step for obtaining a prediction coefficient based on the number of sound connections connected simultaneously, and for calculating a transferable rate based on the prediction coefficient and the number of sound cells to be arriving, a RM cell processing step for processing the RM cells including a transfer rate specified value with which to specify a transfer rate to the data ATM terminal on a transmitting side, a receiving step for receiving the cells, a receiving buffer step for storing received data cells, and a data monitor step for monitoring the arriving condition of the data cells and for calculating a cycle for which the data terminals change the transmission rate.
The ATM traffic controlling method of this invention is characterized by the ATM traffic controlling method, wherein the RM cell processing step may monitor the arriving condition of a backward RM cell, and when the backward RM cell may not be detected, the RM cell processing circuit may automatically transmit the backward RM cell.
The ATM traffic controlling method of this invention is characterized by the ATM traffic controlling method, wherein the RM cell processing step may monitor the arriving condition of the data connections for the data connection, and obtain a cycle for which the data ATM terminals change the transmission rate when the backward RM cell may not be detected and the changed rate.
The ATM traffic controlling method of this invention is characterized by the ATM traffic controlling method, wherein the rate calculation step may automatically correct the prediction coefficient for calculating the number of sound cells to be arriving at the next cycle based on the arriving condition of the sound cells for the plurality of sound connections.
The ATM traffic controlling method of this invention is characterized by the ATM traffic controlling method, wherein the rate calculation circuit may include buffers for storing the sound cells and the data cells separately, and determine the transmission rate of data traffic based on a storing condition of the data cells and the arriving condition of the sound cells in the plurality of sound connections.